It's a log scale graph, it shows a doubling. The performance just isn't increasing as fast as it was before.

yea, buying a pc in the early intel era was a somewhat double edgded sword because you knew that the next generation would come out in a year or so and it would probably have more than double the performance.

For many years my friends and I had a rule that we wouldn't buy a new computer until it offered at least 4X the speed of our old one. We didn't have to wait all that long.